Anisotropic etching is commonly utilized during the fabrication of conductive components for semiconductive circuitry. A prior art process is of anisotropic etching is described with reference to FIGS. 1-4. Referring to FIG. 1, a semiconductor wafer fragment 10 is illustrated at a preliminary step of an anisotropic etching process. Wafer fragment 10 comprises a substrate 12. Substrate 12 comprises a semiconductive material layer 11 and an insulative material layer 15 formed over the semiconductive layer. Semiconductive layer 11 can comprise, for example, monocrystalline silicon lightly doped with a p-type dopant. Insulative layer 15 can comprise, for example, borophosphosilicate glass (BPSG). Substrate 12 comprises a frontside surface 30 and a backside surface 32.
To aid in interpretation of the claims that follow, the term "semiconductor substrate" is defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon) and semiconductive material layers (either alone or in assemblies comprising other materials). The term "substrate" refers to any supporting structure, including, but not limited to, the semiconductive substrates described above.
A tungsten plug 14 is formed within insulative layer 15. Tungsten plug 14 can connect to electrical components (not shown) which comprise integrated circuitry associated with substrate 12. A titanium layer 16 is formed over insulative layer 15 and in contact with tungsten plug 14. An aluminum-copper alloy layer 18 is formed above titanium layer 16, and a titanium nitride layer 20 is formed above layer 18. Together, layers 16, 18 and 20 comprise a composite conductive layer 22. A patterned masking layer 24 is formed over a portion of composite conductive layer 22. Masking layer 24 can comprise photoresist. Masking layer 24 is in a shape of a conductive component which is ultimately to be formed from composite conductive layer 22. For instance, masking layer 24 can be patterned into a shape of a conductive line. Patterned masking layer 24 comprises opposing sidewalls 26 and 28.
Referring to FIG. 2, composite conductive layer 22 is anisotropically etched. At the processing step shown in FIG. 2, composite conductive layer 22 has been partially anisotropically etched to a point at which the etching has proceeded partially through aluminum-copper alloy layer 18. Etching can occur in a reactor having a first powered electrode (not shown) in electrical connection with frontside surface 30, and a second powered electrode (not shown) in electrical connection with backside surface 32. The reactor can be a LAM9600 reactor, in which case the first electrode can be an inductively coupled electrode at 500 watts and the second electrode can be at 250 watts. The wattage is different for different reactors. For instance, in an AME DPS reactor, the first electrode can be at 1500 watts and the second electrode can be at 500 watts.
The anisotropic etch creates a conductive component 34 having sidewalls coextensive with sidewalls 26 and 28 of patterned masking layer 24. As the anisotropic etching proceeds, blocking layers 36 and 38 are formed adjacent sidewalls 26 and 28, and along the sidewalls of the electrical component. Blocking layers 36 and 38 can comprise organic materials, such as carbon-chlorine polymers, as well as inorganic materials. Blocking layers 36 and 38 protect sidewalls of component 34 from being etched and thereby enhance anisotropy of the etch of composite conductive layer 22.
Referring to FIG. 3, the anisotropic etch described with reference to FIG. 2 has completely etched through composite conductive layer 22. Blocking layers 36 and 38 now extend to frontside surface 30 of substrate 12.
Referring to FIG. 4, masking layer 24 (shown in FIG. 3) is removed to leave a conductive component shape 40 of remaining composite component layer 22. Blocking layers 36 and 38 are adjacent conductive component shape 40. Blocking layers 36 and 38 comprise extensions 42 and 44 extending above conductive component 40 and laterally adjacent where masking layer 24 (shown in FIG. 3) was before its removal.
Referring to FIG. 5, blocking layers 36 (shown in FIG. 4) and 38 (shown in FIG. 4) are removed from adjacent conductive component 40. One method of removal of such blocking layers is to utilize a bath of organic solutions to strip layers 36 and 38 from adjacent conductive component 40. Such method is undesirable as the organic solutions are environmentally hazardous and create flammable fumes. An alternative technique for removing blocking layers 36 and 38 is to utilize a phosphoric acid strip. However the phosphoric acid will undesirably etch the aluminum of alloy layer 18.
It would be desirable to develop alternative methods for removing blocking layers from adjacent a conductive component after anisotropically etching to form the conductive component.